Downhole delay assembly for blasting with series delay
US4347789A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 15, 1980 |
| Grant date | Sep 7, 1982 |
| Priority date | — |
| Expiry date | Jul 15, 2000 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF42D1/06
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A downhole delay assembly is provided which can be placed into a blasthole for initiation of explosive in the blasthole. The downhole delay assembly includes at least two detonating time delay devices in series in order to effect a time delay of longer than about 200 milliseconds in a round of explosions. The downhole delay assembly provides a protective housing to prevent detonation of explosive in the blasthole in response to the detonation of the first detonating time delay device. There is further provided a connection between the first and second time delay devices. The connection is responsive to the detonation of the first detonating time delay device and initiates the second detonating time delay device. A plurality of such downhole delay assemblies are placed downhole in unfragmented formation and are initiated simultaneously for providing a round of explosive expansions. The explosive expansions can be used to form an in situ oil shale retort containing a fragmented permeable mass of formation particles.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.